1. Field of the Invention
The present invention relates to a flow control method and a receiving end device of an Ethernet (registered trademark) transmitter, and, more particularly to a flow control method and a receiving end device that treat as a control target, data that includes a set priority.
2. Description of the Related Art
When performing data communication between two network devices using Ethernet (registered trademark) transmission, if an input speed of data into a receiving end device exceeds a processing speed of the receiving end device, a frame wait and a frame rejection of an input buffer are likely to occur. For preventing the frame wait and the frame rejection, a conventional flow control, which uses a pause frame, is disclosed in Japanese Patent Application Laid-open No. 2005-210385. In the conventional flow control using the pause frame, if a number of frames accumulated in the input buffer of the receiving end device exceeds a predetermined threshold, the receiving end device transmits the pause frame to a transmitting end device. Upon receiving the pause frame, the transmitting end device stops an output for a predetermined time period. A stop time period is allocated in the pause frame as a pause time. Upon lapse of the pause time specified in the pause frame, the transmitting end device releases an output stop (pause). The transmitting end device also releases the output stop if the receiving end device transmits the pause frame in which the pause time is “0”.
A shaping device, as disclosed in Japanese Patent Application Laid-open No. 2006-87147, provides a queuing priority for packets and stores the packets of a high priority in the buffer, thereby preventing rejection of the packets of the high priority. Further, by setting the high priority for the packets that are highly important, the shaping device prevents rejection of the important packets.
However, in the flow control, which uses the conventional pause frame mentioned earlier, regardless of high priority data or low priority data, the entire transmission stops during the predetermined time period. Due to this, maintenance of a service class is adversely affected. In other words, in a flow control method using the conventional pause frame, a priority-based control cannot be exercised.
The shaping device, which is disclosed in Japanese Patent Application Laid-open No. 2006-87147, does not control an available space or capacity in the input buffer of a receiving end device. Due to this, an output control cannot be carried out based on the available space in the input buffer of the receiving end device.